What are Hormones

• The Endocrine glands (A part of the Nervous System) within the body secrete hormones, which are chemical messengers.
• The bloodstream is where hormones are secreted, moving to target cells or organs and having a specific effect.
• Hormones perform essential roles in various body functions, such as mood swings, reproduction phenomena, metabolism function, and growth and development within the body.
• An imbalance of hormones in the body can cause many disorders like diabetes, infertility, etc.

Define Hormone

A chemical messenger known as a hormone is created by endocrine glands, which are found in the nervous system. They travel through the bloodstream and bind to specific receptors on target cells, triggering a particular response. They play essential roles in various physiological body functions, such as mood swings, reproduction phenomena, metabolism function, and growth and development within the body.

Co-ordination in Humans

The way the body’s organs and systems are designed to function effectively together is through coordination. For instance, the leg muscles will require more glucose and oxygen if used for running. To meet this demand, the lungs breathe faster and deeper to obtain the excess oxygen, and the heart pumps more rapidly to get the oxygen and glucose to the muscles more quickly. The diaphragm, intercostal muscles, and heart receive neural impulses from the brain when it notices variations in the blood’s oxygen and carbon dioxide content. In this example, the coordination of the systems is brought about by the nervous system.

The extra supplies of glucose needed for running come from the liver. Glycogen in the liver is changed to glucose released into the bloodstream. A chemical called Adrenaline converts glycogen to glucose. The endocrine system brings about coordination by chemicals. The endocrine system depends on releasing chemicals, called hormones, from endocrine glands. The bloodstream carries hormones. For instance, the circulatory system has insulin secreted in the pancreas.

Types of Hormones

Several types of hormones occur in nature. Every specific hormone performs its specific function in the body. The types of hormones are given below:

Amino acid-derived hormones

Amino acid-derived hormones are a type of hormone that is derived from amino acids. They have a more straightforward structure than peptide hormones and can act quickly on target tissues, such as adrenaline, thyroid hormones, and Melatonin.

The “fight or flight” reaction or stress is controlled by adrenaline or epinephrine, created by adrenal glands. Adrenaline attaches to receptors on the exterior of cells, setting off a chain of metabolic processes that increase breathing, blood pressure, and heart pumping rate as the body gets ready for exercise.

Thyroxine (T4) and triiodothyronine (T3), which control metabolism are secreated by Thyroid gland. They bind to receptors inside cells, directly affecting gene expression and protein synthesis. For healthy growth and development, thyroid hormones are crucial for controlling body temperature and energy consumption.

The body’s sleep and wake cycles are controlled by Melatonin which is secreted by the Pineal gland. It comes from the amino acid tryptophan and is released in response to darkness, encouraging tiredness.

Overall, amino acid-derived hormones are critical in regulating various physiological processes and maintaining homeostasis. Imbalances or dysregulation of these hormones can lead to multiple health problems.

Peptide hormones

Combined, short chains of amino acids provide the building blocks of peptide hormones, a particular class of hormones. Endocrine glands in the body secrete them. Oxytocin, growth hormone, and insulin are some examples of peptide hormones.

When peptide hormones connect to particular receptors on the surface of target cells, a series of intracellular signaling pathways are activated, ultimately resulting in a specific bodily reaction. For example, insulin boosts the liver, muscles, and fatty tissue to absorb glucose from the blood, get energy, or keep it as glycogen or fat by attaching to receptors on their surfaces.

The Pituitary gland produces growth hormones. They are used for the growth & development of the body. It binds to receptors on various tissues, stimulating the synthesis of proteins and the proliferation of cells.

The hypothalamus secretes oxytocin. It plays a role in social bonding. It binds to receptors in the breast tissue, stimulating milk let-down during breastfeeding, and also plays a role in maternal behavior and social bonding.

The regulation of numerous physiological processes, such as metabolism, growth, and reproduction, is greatly aided by them. Diabetes, development abnormalities, and infertility can result from imbalances or dysregulation of these hormones.

Protein hormones

The body’s endocrine glands create a type of hormone called a protein hormone. They consist of long chains of amino acids compared to peptide hormones and have a more complex structure. For instance, Follicle-stimulating (FSH), luteinizing (LH), and thyroid-stimulating hormones (TSH).

When protein hormones connect to particular receptors on the surface of target cells, a series of intracellular signaling pathways are activated, ultimately resulting in a specific bodily reaction. For example, FSH and LH are produced by the pituitary gland and regulate the reproductive system. FSH promotes the growth and maturation of ovarian follicles in females and the production of sperm in males. At the same time, LH stimulates ovulation in females and testosterone production in males.

The pituitary gland produces TSH, which ceduses thyroid gland to secrete hormones by attaching to receptors on the surface of thyroid cells.

Growth, development, and reproduction are only a few of the physiological processes that protein hormones control. Imbalances or dysregulation of these hormones can lead to multiple health problems, such as infertility and thyroid disorders.

Steroid hormones

The adrenal glands and the gonads, among other endocrine glands, create steroid hormones derived from cholesterol (testes and ovaries). For example, estrogen, testosterone, and cortisol.

Because they are lipophilic (fat-soluble), steroid hormones can easily permeate through cell membranes. Once within the cell, they attach to particular receptors in the cytoplasm or nucleus to create a hormone receptor complex. This complex binds to specific DNA sequences, regulating gene expression and protein synthesis.

The Adrenal glands produce Cortisol. It controls several physiological functions like metabolism, immunological, and stress response. It binds to receptors in multiple tissues, promoting the breakdown of proteins and fats for energy and suppressing immune function.

Male testicles create testosterone, which supports male sexual maturation and reproduction. Moreover, it affects bone density and muscle mass. Women’s ovaries produce estrogen, which encourages female sexual development and reproduction. Also, it affects how healthy the heart and bones are.

They control several physiological functions like growth, reproduction, and metabolism. Cushing’s syndrome, infertility, and osteoporosis, can result from imbalances or dysregulation of these hormones.

Eicosanoid hormones

Eicosanoids are signaling molecules, secreted by arachidonic acid which is polyunsaturated fatty acid by nature. Platelets, endothelial cells & White blood cells create eicosanoids.

Eicosanoids regulate inflammation, blood flow, and other physiological processes. Leukotrienes, lipoxins, thromboxanes, and prostaglandins are their four influential groups.

Prostaglandins are involved in regulating inflammation, blood flow, and the formation of blood clots. They are created by various cells, including the lining of blood arteries and white blood cells.

Thromboxanes are involved in regulating blood clotting and vasoconstriction. They are produced by platelets and promote platelet aggregation and blood clot formation.

Leukotrienes are involved in regulating inflammation and the immune response. They can result in vasoconstriction, bronchoconstriction and lung mucus formation. They are secreted by white blood cells.

Lipoxins are involved in resolving inflammation and promoting tissue repair. They are produced by white blood cells and help limit the inflammatory response’s duration and severity.

Eicosanoids regulate various physiological processes, including inflammation and blood flow. Their imbalance can cause Asthma, cardiovascular disease, and arthritis.

Gasotransmitter hormones

Little gaseous molecules called gasotransmitters serve as signaling molecules in the body. Three important gasotransmitter hormones are:

• Nitric oxide
  Nitric oxide is a gasotransmitter hormone that regulates blood pressure, neurotransmission, and immune function. Various cell types produce it, including immunological, endothelial, and neuronal cells.
• Carbon monoxide
  The gasotransmitter Carbon monoxide (CO) has been demonstrated to control inflammation, blood pressure, and neurotransmission. It is produced in the body through the breakdown of heme by the enzyme heme oxygenase.
• Hydrogen sulfide
  Anti-inflammation, vasodilation, and cytoprotection in the body are due to Hydrogen sulfide (H₂S). It is created by cystathionine gamma-lyase and cystathionine beta-synthase enzymes.

Peptide Hormones

Combined, short chains of amino acids provide the building blocks of peptide hormones, a particular class of hormones. Endocrine glands in the body secrete them, transfer them to target cells, where they attach to particular receptors on the cell’s surface.

The structure of peptide hormones varies, but they all share some common characteristics. They are typically between three and fifty amino acids long and have a molecular weight of fewer than 10,000 daltons. They are often synthesized as larger precursor molecules processed by enzymatic cleavage to produce the active hormone.

A series of amino acids connected by peptide bonds make up peptide hormones. The sequence of amino acids determines the characteristics of hormones, like their capacity to bind to receptors, biological activity, and stability in the body.

Because peptide hormones are often water-soluble and cannot cross cell membranes, they must attach to specific receptors there. A signalling cascade within the cell is set off by the binding of the hormone to its receptor. It eventually results in modifications to gene expression, protein synthesis, or other cellular activities.

Adrenocorticotropic hormone

In response to hypothalamic signals, the pituitary gland (anterior part) produces Adrenocorticotropic hormone or Corticotropin. Encouraging the adrenal glands to make and remove cortisol makes ACTH essential for the body’s stress response.

• ACTH is a polypeptide hormone made up of 39 amino acids.
• It is secreted in the stress condition.
• ACTH acts on the adrenal cortex, specifically the zona fasciculate and zona reticularis, to stimulate the synthesis and secretion of cortisol.
• The body’s stress response depends heavily on the steroid hormone cortisol. Elevating blood sugar, reducing immunological function, and releasing energy reserves aid the body’s reaction to stress.
• Disorders of the HPA axis can lead to abnormal ACTH levels and cortisol production. For instance, Cushing’s syndrome is characterized by excessive cortisol production. In contrast, Addison’s disease is characterized by inadequate cortisol production and may be brought on by harm to the pituitary or adrenal glands.
• ACTH levels can be measured in blood and urine tests to help diagnose disorders of the HPA axis. Compared to a high ACTH level, Addison’s disease may be indicated by a low ACTH level.

Atrial natriuretic peptide

Atrial natriuretic peptide, or ANP, is secreted by the Heart’s atria, which control the body’s fluid balance and blood pressure.

• ANP is a peptide hormone composed of 28 amino acids.
• ANP is released in response to increased blood volume and pressure in the Heart. This triggers the release of ANP from the atrial myocytes.
• ANP acts primarily on the kidneys to increase urine production and excretion of sodium and water.
• ANP is critical in regulating blood pressure and fluid balance in the body. It works by decreasing sodium and water reabsorption in the kidneys, which increases urine output and reduces blood volume and pressure.
• Abnormal levels of ANP cause many health conditions, including heart failure, hypertension, and kidney disease.
• ANP levels can be measured in blood and urine tests to help diagnose particular heart and kidney conditions.

Calcitonin

The thyroid gland secretes the calcitonin hormone. It controls calcium and phosphate metabolism in the body and is called Calcitonin.

• It is a peptide hormone composed of 32 amino acids.
• High blood calcium levels cause the parafollicular thyroid gland cells to generate and secrete Calcitonin.
• It hinders calcium release from bone & calcium absorption in the intestines. It increases calcium excretion in the kidneys.
• It lowers blood calcium levels, reversing the parathyroid hormone effects, which raise calcium levels in the blood.
• Abnormal calcitonin levels have been associated with certain health conditions, including thyroid cancer.
• Calcitonin levels can be measured in blood and urine tests to help diagnose thyroid cancer and monitor treatment.

Calcitonin Function

It controls the body’s calcium metabolism. It functions by preventing osteoclasts from consuming bone tissue and releasing calcium into the bloodstream from doing their job. So, it decreases the calcium level in the blood & increases calcium in bone tissue. Moreover, calcium-tonin’ promotes calcium excretion in the kidneys while decreasing calcium absorption in the intestines.

Calcitonin gene related Peptide

The neuropeptide calcitonin gene-related peptide (CGRP) controls circulatory, inflammatory, and pain processes. It is secreted from the calcitonin gene. In response to various stimuli, such as inflammation, injury, and stress, sensory nerves release CGRP, which is widely distributed in the central and peripheral nervous systems. CGRP contributes to vasodilation, lowers blood pressure, and guards against ischemia harm to the heart and brain.

Calcitonin Salmon

It is a synthetic form of calcitonin, created naturally in the thyroid glands of animals like salmon. Calcitonin salmon works by reducing the activity of the cells that break down bone tissue, called osteoclasts. Reduced bone resorption results can assist in preventing bone loss and lowering the risk of fractures. Infrequently, calcitonin salmon may result in allergic responses, low blood calcium levels, and the common adverse effects of nausea, vomiting, and flushing.

Cholecystokinin

Cholecystokinin is secreted by small intestinal cells when food is in the small intestine, specifically fatty foods. It is essential for digestion and controlling hunger.

• CCK is produced and released by cells called I-cells located in the lining of the small intestine and the duodenum. It is released into the bloodstream and travels to target cells throughout the body.
• It exists in two different varieties: CCK-8 and CCK-33. CCK-8 is the most common form and comprises eight amino acids, while CCK-33 comprises 33.
• It controls stress and anxiety as a neurotransmitter in the brain.
• Gallbladder disease and pancreatic insufficiency are two digestive illnesses caused by the abnormality of cholecystokinin level.
• A complex interplay of hormones and nervous system signals regulates CCK. Various factors can affect its secretion, including food in the digestive tract, stress, and certain medications.

Functions of Cholecystokinin

• It encourages the pancreas to produce enzymes (digestive in nature) in the small intestine for the breakdown of food.
• Cholecystokinin causes the gallbladder to constrict, releasing bile into the small intestine to help in fat breakdown.
• Cholecystokinin signals the brain to decrease hunger and promote feelings of fullness, hence reducing appetite.

Somatostatin

Somatostatin is a hormone manufactured by the hypothalamus, pancreas, and gastro intestine. It is essential for controlling numerous physiological functions, such as the neurological, endocrine, and digestive systems.

• Somatostatin affects target cells all over the body by attaching to particular receptors. There are five subtypes of somatostatin receptors (SSTR1-5), each with different bodily functions and distributions.
• Several factors, including nutrients in the digestive tract, neurotransmitters, and other hormones, regulate Somatostatin. It is also regulated by negative feedback mechanisms, where the hormone can inhibit its secretion.
• Somatostatin dysfunction or abnormal levels have been linked to several illnesses and conditions, including acromegaly, diabetes, and cancer. Somatostatin analogs, synthetic versions of the hormone, treat several conditions, including acromegaly, carcinoid tumors, and neuroendocrine tumors.

Functions of Somatostatin

• Somatostatin controls the production of several hormones, like thyroid-stimulating, insulin, growth hormone, and glucagon.
• Somatostatin inhibits digestive enzyme secretion and slows food movement through the digestive tract.
• Somatostatin prevents the production of glucagon and insulin, which aids in controlling blood sugar levels.
• Somatostatin contains anti-inflammatory effects and can control inflammatory cytokine release, reducing inflammation.

Secretin

Secretin is produced by duodenum cells. It controls digestion by encouraging the pancreas to secrete bicarbonate and the liver to discharge bile.

• Secretin is produced in the duodenum when acidic chyme is present in it. Acidic chyme stimulates the production of secretin in the duodenum & then transfers to the pancreas and liver, promoting the secretion of bile and bicarbonate.
• Although its precise involvement in this regard needs to be better explored, secretin is also thought to contribute to regulating the body’s water and electrolyte balance.
• Abnormalities in secretin cause diseases like pancreatic insufficiency, celiac disease, and multiple forms of cancer. Secretin stimulation tests, which involve administering secretin and monitoring pancreatic and liver function, are used to diagnose certain digestive disorders, including pancreatitis and pancreatic cancer.

Functions of Secretin

• Secretin neutralizes the acidic chyme (partially digested food) that enters the small intestine from the stomach.
• Secretin stimulates the liver to secrete bile, which helps to emulsify fats in the small intestine.
• Secretin inhibits gastric acid secretion by the stomach, which helps to protect the duodenum from acidic chyme.

Relaxin Hormone

Relaxin is a hormone produced by the corpus luteum during the pregnancy period & ovaries in non-pregnant women and the testes in males. It maintains some systems in the body like cardiovascular, musculoskeletal, and reproductive systems.

• Relaxin acts by binding to specific receptors on target cells throughout the body. There are two main subtypes of relaxin receptors (RXFP1 and RXFP2), each with different bodily functions and distributions.
• Abnormalities in relaxin lead to preterm labor, preeclampsia, and certain types of cancer.
• Relaxin plays an important role in preparing the body of the mother for childbirth by relaxing the pelvic ligaments and softening the cervix. This allows for easier passage of the baby through the birth canal.
• Relaxin is involved in regulating menstrual cycles and may help regulate the timing of ovulation.
• It stimulates the growth of new blood vessels which is useful for wound recovery and tissue repair.
• It shows vasodilatory effects which lower blood pressure and improve blood flow within the body.

Neuropeptide Y

It is a peptide neurotransmitter which is filled in both the central and peripheral nervous systems. It controls anxiety, heart function, stress response, and hunger management.

• The neuropeptide family, which also includes the peptides YY (PYY) and pancreatic polypeptide, comprises the 36 amino acid peptide known as NPY (PP). With only a few amino acid variations between humans and rodents, the structure of NPY is remarkably maintained across species.
• NPY is one of the most potent appetite stimulants known, and its levels in the brain are elevated during fasting and decreased after feeding. It acts on the hypothalamus, where it increases food intake and reduces energy expenditure.
• In the stress response, NPY has a role in lowering anxiety and stress-related behaviours. It is released in reaction to stressors, such as physical or mental stress.
• NPY influences the control of cardiovascular function, raising blood pressure and heart rate as a result. It is released from sympathetic nerve terminals and acts on Y1 and Y2 receptors located on vascular smooth muscle cells to cause vasoconstriction and increase blood pressure.
• NPY has been implicated in the regulation of anxiety and other mood-related behaviours. It operates the hippocampus, amygdala, and other parts of the brain.
• Obesity, hypertension, anxiety disorders, and depression are due to their imbalance. Drugs that target NPY receptors are being developed for the treatment of these diseases.

Melanocyte stimulating hormone

It is produced by the Pituitary gland named Melanocyte stimulating hormone. The body uses MSH for a variety of purposes, including controlling skin pigmentation and modifying immune system activity.

• Proopiomelanocortin, a precursor protein, produces the 13-amino acid peptide known as MSH (POMC). POMC is the building block for beta-endorphin and adrenocorticotropic hormone.
• The body uses MSH for a variety of purposes, including controlling skin pigmentation and modifying immune system activity.
• MSH is a strong melanin synthesis stimulant and is what causes the skin to tan in response to UV light. MSH increases the generation and release of melanin into neighbouring skin cells by acting on melanocytes, the cells that make melanin.
• Skin conditions like vitiligo, a condition where the loss of melanocytes results in areas of depigmented skin, have been linked to abnormalities in MSH synthesis or signalling. MSH analogues have been created for the treatment of skin conditions and could be used to treat diseases with an immunological component.

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